Electrowetting is a microfluidic phenomenon that modifies the shape of a liquid in relation to a surface by applying an electrical field, e.g. by applying a voltage across two electrodes. For example, if the surface is hydrophobic, the electrical field causes a change in the shape of the liquid that appears to change the wetting properties of the hydrophobic surface. If the fluid(s) in an electrowetting cell and some of the wall(s) around the fluid(s) are sufficiently transparent, the electrowetting cell may be used as an electrically controllable optic. Such optics have recently been the subject of a widening scope of light processing applications, such as variable lenses, variable prisms, optical switches, displays, etc.
Electrowetting lenses, for example, are conventionally used in the camera industry. These lenses tend to be very small (several millimeters) and operate in a small tunable range (small range of output light angle). The thickness of the lenses are also typically less than half the lens size. An electrowetting cell structure for a lens for a camera application or the like, e.g. to selectively focus light input to an image sensor or to selectively control beam distribution of a flash, typically supports only beam shaping.
There have been proposals to develop variable optical prisms using electrowetting cell arrangements. An electrowetting lens may have various different shaped structures, e.g. round, square or rectangular. An electrowetting prism normally is square or rectangular. The overall working principle for either beam shaping or steering is the same—the voltage applied across the dielectric layer attracts the conducting liquid so as to change the wetting area of the cell and thus the shape of the liquid(s) in the cell.